Question for Polar Power users

I have an older wired Polar power setup ( S625x). The fastest logging interval is every 5 seconds. Do any of you have an idea of how this logging rate affects the accuracy of your peak power readings versus the other meters that log a 1 sec intervals.

When doing my sprint intervals I would prefer to not look at the display to see my peak power yet when I look at the downloaded data the logged value is much lower than what would expect. I have been using my max speed on my cyclo-computer the determine whether I am doing them hard enough but wind and incline can make a huge difference.

Any insight is appreciated.